Powering a computer, Xbox

Why make things more difficault....i would just tap into your cigarette lighter line behind the dash and run the wire to your trunk. like fuseblower said.. save time. and then you know it would be hooked up to your battary corectley

Just my $0.02 worth on this one. I wouldn't necessarily connect directly to your cigarette lighter without first considering what you'll be using that circuit for. For example, I've got a 160 watt inverter that's got a 20 amp fuse on it. If you're going to use anything larger than that, chances are it's also got a larger fuse. Consider, then, whether or not you'll be using your cigarette lighter to power anything more demanding than a cell-phone charger or a radar detector....at ANY time. If your answer to that question is yes, then you need to run a separate +12v line to the battery for the inverter, and would also benefit from a switch of some sort (or a relay to function as one). You can get an auxilliary cigarette lighter jack at most Wal-Mart or K-Mart type stores for a very reasonable amount, and you can ground it directly to the body of your vehicle. This will give you a cigarette lighter jack to plug into, which will keep you from having to hack the inverter to connect it to power. If you're using a switch, I'd place it under the dash somewhere convenient yet out of the way to help keep you from accidentally bumping it. If you're using a relay, follow the wiring diagrams on this site, they'll help you a lot towards getting it wired right. I mention this because most cigarette lighters aren't rated over 25-30 amps, and I wouldn't want you to start having problems with your equipment unnecessarily. Pay attention to what you're connecting where, and try to make sure you're not hacking up whole units (unless you're comfortable with that sort of thing and sure you won't cause damage), and you should be in good shape. Remember, though, that if you cause any problems with your vehicle, noone here is responsible for your mistakes. We all make mistakes at some point, the idea is to limit the damage they can cause...that's why fuses are made. Good luck!!